Method of improving papermaker&#39;s felt



United States Patent M 3,463,657 METHOD OF IMPROVING PAPERMAKERS FELT Wilhelm Schuster, Frankfurt am Main, Germany, assignor to Forschungsgemeinschaft der Deutschen Filztuchindustrie, Frankfurt am Main, Germany N0 Drawing. Filed Oct. 27, 1965, Ser. No. 505,401 Claims priority, applicFation Germany, Feb. 17, 1965,

Int. Cl. C08c 17/16; 1344a 1/44, 1/20 US. Cl. 117--65.2 3 Claims ABSTRACT OF THE DISCLOSURE This invention relates to the manufacture of non-woven felt fabrics.

For some years, felts, especially papermakers felts, have been made by securing textile fibers to woven base fabrics by means of felting needles.

Such felting needles make it possible to needle thick naps onto relatively light-base fabrics or on synthetic fibers blended with natural fibers. The thus obtained attachment or anchoring of the nap in the base fabric is not firm enough for paperrnakers felts. The entanglement of the fibers produced by the needling and the adhesion of the fibers needled through the threads of the base fabric is mostly insufficient for practical applications. Frequently, the surface layer becomes detached from the base fabric after short operations, or the loss of fibers is so great as to produce markings.

Procedures have been developed in order to fasten the needled fibers still more firmly in the base fabric or to improve their strength and cohesion by interfiber entanglement, e.g., by incorporating into the nap to be needled a certain amount of fibers which on heating with steam or in boiling in water undergo strong shrinkage and thereby densifies the felt; however, this procedure is expensive and cannot be always applied.

In another procedure, the lower side of needled felts is passed over a gas flame, whereby part of the projecting fibers melt. This procedure has the drawback that it can be applied only to said needled felts Which have a surface of synthetic fibers because Wool or cotton fibers would be destroyed at the required high temperatures.

I have found a procedure which does not present the recited drawbacks. In my novel process, I accomplish a sufficiently firm anchoring of the surface layer in the base fabric by bonding the fibers of the underside of the felt with an elastic adhesive at their points of intercrossings and contacts in such a way as to avoid any interference with the drainage of water.

In carrying out the invention, felt fabric, which may be needled, is coated at its underside with a water insoluble elastic adhesive layer of even thickness; subsequently the coated felt is compressed and then treated on the coated surface with a strong jet of compressed air. Thereby, films or membranes which may have been formed by the adhesive which still contains the solvent, are broken up, and the adhesive is distributed in the felt in such a way that, after releasing the compression pressure and after the treatment with the compressed air, adhesive remains only on the individual fibers and particularly at their 3,463,657 Patented Aug. 26, 1969 points of contact without penetrating to the upper side of the felt fabric.

The adhesive may be applied to the underside of the felt by any conventional method, e.g., by spraying, by a doctor blade, or by running the felt. over or between applicator rolls. The mechanical compression of the felt is than also carried out in any suitable manner, e.g., by means of two rollers rotating in opposite directions.

In order to shorten the drying of the felt to which the adhesive has been applied, compressed air of slightly elevated temperature may be employed.

After the compressed air treatment but before the adhesive is completely dried, the felt may be subjected again to a compression treatment, for instance by means of two rollers, in order to bind the adhesively coated fibers at additional points of contact.

In a preferred embodiment of the invention, a needled papermakers felt is compressed between two vertically superposed metal rollers, the lower one of which carries an adhesive layer of a water-insoluble elastic adhesive such as butadiene-acrylonitrile or 2-chlorobutadiene, kept at a constant thickness by means of a doctor; since the rollers compress the felt, the adhesive penetrates its lower layers and envelops the fibers. When the felt has left the rollers, the fibers coil back into their original bulky position. The adhesive membranes left between many of the fibers are then torn by means of strong compressed air jets whereby the adhesive remains especially at the points of contact and intercrossing of the fibers.

Papermakers felts whose fibers at the underside had been treated by the procedure set forth hereinabove, did hardly shed any fibers during operation, and their running properties in the paper-machine were improved. Felts once adjusted did not require any re-adjustment. This is believed to be due to the good adhesion of the elastic adhesive on the surfaces of the rollers.

Even non-needled papermakers felts whose underside had been treated in accordance with the invention proved to be superior to conventional felts with respect to dimensional stability, service properties and fiber adhesion.

I claim:

1. A method of improving the properties of papermakers felt comprising applying a coating of uniform thickness of a water-insoluble adhesive elastomer solution to the underside only of the felt, compressing the felt, and treating the adhesively coated underside of the felt with a jet of compressed air to break films of the adhesive elastomer between fibers of the felt and leave the adhesive elastomer at the underside of the felt only on individual fibers and at points of contact of the fibers.

2. The method as claimed in claim 1 including the step of allowing the surface fibers of the felt, prior to application of the compressed air jets, to coil back into their original bulky condition.

3. The method as claimed in claim 2 comprising subjecting the felt, after it had been subjected to said compressed air treatment but before the adhesive is completely dry, to a second compression treatment.

References Cited UNITED STATES PATENTS 1,328,541 1/1920 Palmer 11765.2 2,064,360 12/1936 Schur 117-65.2 3,075,274 1/ 1963 MiZell.

WILLIAM D. MARTIN, Primary Examiner M. LUSIGNAN, Assistant Examiner US. Cl. X.R. 117-98, 

